330 Proceedings of the British Association. 



deduced from the numbers given by Poisson, that it was much 

 greater ; that a cloud would be colder and not hotter than the 

 surrounding air, and therefore the violent ascending vortex calcu- 

 lated upon by Mr. Espy would not exist. Prof Forbes had three 

 objections to Mr. Espy's theory : 1st. the small funnel at the 

 centre of a tornado, through which Mr, Espy supposed the air to 

 rise, would be insufficient to vent all the air which would rush 

 during a tornado, with the frightful velocity we know it to attain, 

 through the constantly enlarging rings surrounding that central 

 funnel, to the extent of many hundred miles. 2. As the tornado 

 had a progressive motion, as Mr. E. admitted, it would be more 

 difficult than Mr. E. supposed to deduce from the way in which 

 the trees in its path were thrown, the actual course of the atmos- 

 pheric particles at any instant, as each would move with a mo- 

 tion compounded of two motions, both varying in relative direc- 

 tion and magnitude, 3, All the vapor in the air would be con- 

 densed into cloud much sooner than Mr, E. supposed, and he 

 thought it certain that the small amount of heat given out by the 

 vapor would not suffice to expand the air in the funnel to the 

 extent required, if Mr. Espy's views were correct. As to the 

 question whether Mr, Redfield's and Col. Reid's theory of a whirl, 

 or Mr, Espy's radial theory, was most accordant with fact, Mr. 

 Osier said, that from the investigation he had given this subject, 

 he was convinced that the centripetal action described by Mr. E. 

 took place in most hurricanes. The particulars which he, (Mr. O.) 

 had collected, together with the indications obtained from the 

 anemometers at Birmingham and Plymouth, satisfied him that the 

 action of the great storm of January 6 and 7, 1839, was not ro- 

 tatory at the surface of the earth, when it passed across England. 

 He differed, however, both from Mr. Espy and Mr. Redfield in 

 one essential point, for he believed it would be almost impossible 

 to have a violent hurricane without, at the same time, having 

 both rotatory and centripetal action. A storm might very probably 

 be generated in the first instance in the manner accounted for by 

 Mr. Espy, or by the action of contrary currents : in the first case 

 the rush of air toward a spot of greater or less diameter would 

 not be perfectly uniform, owing to the varying state of the sur- 

 rounding atmosphere ; this together with the upward tendency 

 of the current would, in some cases, produce a violent eddy or 

 rotatory motion, and a whirlwind of a diameter varying with the 



